The current organic light emitting diode (OLED) display device is a device for graphical display by use of a reversible discoloration phenomenon produced by an organic semiconductor material driven by current. OLED display device has advantages such as ultralight, ultrathin, high brightness, large view angle, low voltage, low power consumption, fast response, high definition, antiknock, flexibility, low cost, simple process, less use of raw materials, high luminous efficiency and wide temperature range, and is considered as the most promising next-generation display technology.
OLED device generally includes a cathode, an anode and an organic light-emitting layer sandwiched between the cathode and the anode. Under the externally applied voltage, electrons are injected from the cathode into the organic light-emitting layer and holes are injected from the anode into organic light-emitting layer, and in organic light-emitting layer, the electrons and the holes meet and recombine to produce excitons, i.e., radiating light. In a process of manufacturing OLED devices, especially large size OLED devices, the organic light-emitting layer may be mixed with foreign matters, and due to the small distance between the cathode and the anode, say about 0.3 μm, in the vacuum lamination process, the foreign matters are likely to pierce the membrane of the cathode or the anode under high pressure, which causes a short circuit between the cathode and the anode. Therefore, the whole pixel cannot be lit, dark spot occurs, and the display quality is severely affected.
At present, it is comparatively difficult to limit the size of the foreign matters to below 0.3 μm by means of in-process quality control, so it is hard to reduce dark spots produced by the foreign matters.